This invention relates to a three-phase-in-one type gas insulated switchgear apparatus for used in electric power transmission/distribution and reception/distribution and, more particularly, to a three-phase-in-one type gas insulated switchgear apparatus of which single phase voltage transformer is disposed in one phase of three phases.
FIG. 7 is a cross-sectional view of a conventional gas insulated switchgear apparatus such as disclosed in Japanese Patent Publication No. 6-30525. FIG. 8 is a cross-sectional view taken along line VIII--VIII of FIG. 7, where, the hatching for the cross section is omitted. In FIGS. 7 and 8, 1 is breakers, 1a is a breaker vessel, 2 and 3 are grounding switchgears, 4 is a current transformer, 5 is a control box, 6 and 7 are main bus bars, 8 and 9 are disconnectors, 10 are cable heads, 10a are disconnectors, 10b is a connection portion between the breaker vessel 1a and the disconnector vessel 10a, 11 are lightning arresters, 12 is a voltage transformer, 13 are disconnectors, 14 is a grounding switchgear, 15 is a support bed and 16 are cables. L.sub.1 is a unit (gas insulated switchgear apparatus) length, D.sub.1 is a flange diameter of the disconnector vessel 10a and H.sub.1 is a unit height.
Further, in the breaker vessel 1a, the breakers 1 of three phases, grounding switchgears 2, 3 of three phases and the current transformer 4 of three phases are housed. Also, within the breaker vessel 10a, the cable heads 10 of three phases, the lightning arresters 11 of three phases, the single phase voltage transformer 12, the disconnectors 13 of three phases and the grounding switchgears 14 of three phases are accommodated. Further, the cable heads 10, the lightning arresters 11 and the voltage transformer 12 are disposed in parallel in the lower portion of the disconnector vessel 10a. The disconnectors 13 are disposed in the upper portion of the disconnector vessel 10a and the connection portions 10b are disposed in the upper portions of the breaker vessel 1a and the disconnector vessel 10a.
FIG. 9 is a cross sectional view of a conventional gas insulated switchgear apparatus disclosed in a copy of a microfilm of Japanese Utility Model Laid-Open No. 61-126719, for example. In FIG. 9, the structural components are similar to those of the prior art example 1, to that their description is omitted. However, the voltage transformers 12 are disposed one for each of the three phases.
Then, the disconnector vessel 10a accommodates therein the current transformers 4 of three phases, the cable heads 10 of three phases, the lightning arresters 11 of three phases, the voltage transformer 12 of three phases and the disconnectors 13 of three phases. Further, the cable heads 10 and the lightning arresters 11 are disposed in parallel in the lower portion of the disconnector vessel 10a, and the voltage transformers 12 are disposed in the upper portion of the disconnector vessel 10a. The current transformers 4 are disposed in internal contact with the connection portion 10b of the disconnector vessel 10a. The disconnectors 13 are disposed in the middle portion of the disconnector vessel 10a and the connection portion 10b is disposed in the middle portions of the disconnector vessel 10a and the disconnector vessel 10a.
Further, in the conventional gas insulated switchgear apparatus disclosed in a copy of the microfilm of the Japanese Utility Model Laid-Open No. 61-126719, the installation layout of the three phase lightning arresters 11 and the three phase voltage transformer 12 of FIG. 9 are interchanged. More specifically, the cable heads 10 and the voltage transformers 12 are disposed in parallel in the lower portion of the disconnector vessel 10a and the lightning arresters 11 are disposed in the upper portion of the disconnector vessel 10a.
Since the conventional gas insulated switchgear apparatus has the structure as above described, the cable heads 10, the lightning arresters 11, the voltage transformers 12 and the disconnector 13 are accommodated within the single disconnector vessel 10a, the problem of having separate vessel one for each devices is solved, but another problem as will be discussed below was posed.
In the prior art example 1, the cable heads 10, the lightning arresters 11 and the voltage transformers 12 are disposed in parallel In the lower portion of the disconnector vessel 10a, the diameter D.sub.1 of the disconnector vessel 10a becomes large and the disconnection of the lightning arresters 11 and the voltage transformers 12 with respect to the current path (for example, the electrical disconnection from the electric path or the mechanical dismounting from the disconnector vessel 10a of the lightning arresters 11 and the voltage transformers 12 upon their withstanding voltage test) is difficult.
In the prior art example 2, when the three phase lightning arresters 11 and the three phase voltage transformers 12 are to be contained within the disconnector vessel 10a, the diameter of the disconnector vessel 10a may be decreased. However, when the three phase lightning arresters 11 or the single phase voltage transformer provided for one of the three phases are to be accommodated within the disconnector vessel 10a, the upper portion of the disconnector vessel 10a has a larger unoccupied space as compared to the lower portion, posing a problem that the diameter of the disconnector vessel 10a is unnecessarily large. Also, since the lightning arresters 11 and the voltage transformers 12 are arranged in the position opposing to each other with the disconnectors 13 interposed therebetween, making it difficult to obtain an easy access to the current path of the lightning arresters 11 and the voltage transformers 12.